Prefix the poll result enumerators, report a reset after connect as ECONNRESET, and test the set_sockaddr contract on host

tests/integration/fixtures/socket_set_sockaddr.yaml

@@ -0,0 +1,18 @@
+esphome:
+  name: socket-set-sockaddr
+  on_boot:
+    then:
+      - lambda: |-
+          // Exercise the contract callers rely on: 0 for text that is not an
+          // address, the sockaddr length otherwise, broadcast included
+          struct sockaddr_storage addr;
+          auto *sa = reinterpret_cast<struct sockaddr *>(&addr);
+          ESP_LOGI("test", "SET_SOCKADDR invalid=%u valid=%u broadcast=%u",
+                   (unsigned) socket::set_sockaddr(sa, sizeof(addr), "not an address", 1234),
+                   (unsigned) socket::set_sockaddr(sa, sizeof(addr), "192.0.2.1", 1234),
+                   (unsigned) socket::set_sockaddr(sa, sizeof(addr), "255.255.255.255", 1234));
+
+host:
+api:
+logger:
+  level: INFO

tests/integration/test_socket_set_sockaddr.py

@@ -0,0 +1,45 @@
+"""Integration test for the socket::set_sockaddr failure contract.
+
+Callers skip an address when set_sockaddr returns 0, so text that is not an
+address must return 0 while a real address, including the broadcast address
+that inet_addr() would have reported as a failure, returns its length.
+"""
+
+import asyncio
+import re
+
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_socket_set_sockaddr(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """set_sockaddr reports an invalid address with 0 and accepts broadcast."""
+    loop = asyncio.get_running_loop()
+    result: asyncio.Future[tuple[int, int, int]] = loop.create_future()
+
+    def on_log_line(line: str) -> None:
+        match = re.search(
+            r"SET_SOCKADDR invalid=(\d+) valid=(\d+) broadcast=(\d+)", line
+        )
+        if match and not result.done():
+            result.set_result(tuple(int(g) for g in match.groups()))
+
+    async with (
+        run_compiled(yaml_config, line_callback=on_log_line),
+        api_client_connected() as client,
+    ):
+        assert (await client.device_info()).name == "socket-set-sockaddr"
+        try:
+            invalid, valid, broadcast = await asyncio.wait_for(result, timeout=10.0)
+        except TimeoutError:
+            pytest.fail("SET_SOCKADDR marker never appeared")
+
+    assert invalid == 0
+    assert valid > 0
+    assert broadcast == valid